Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!att!ucbvax!ulysses!ulysses.att.com!mwb
From: mwb@ulysses.att.com (Michael W. Balk)
Newsgroups: comp.lang.c++
Subject: Re: constructors and initializers
Summary: Assignment in constructor OK!
Keywords: constructor, default, class, array, definition
Message-ID: <14758@ulysses.att.com>
Date: 11 May 91 22:42:31 GMT
References: <1991May2.165955.28385@iitmax.iit.edu> <701@taumet.com> <1991May8.155352.18313@alias.com>
Sender: netnews@ulysses.att.com
Lines: 38

In article <1991May8.155352.18313@alias.com>, rae@alias.com (Reid Ellis) writes:
|  A note about initializers in constructors.  Recently, the following
|  class was mentioned under the subject line "HELP: default constructor
|  for array of class":
|  
|  	class Point {
|  		int x;
|  	public:
|  		Point() { x = 200; }
|  		Point(int xc = 100) { x = xc; }
|  	};
|  
|  Not to belabor the point [pun intentional] but the constructors should
|  be written as:
|  
|  	class Point {
|  		int x;
|  	public:
|  		Point() : x(200) {}
|  		Point(int xc = 100) : x(xc) {}
|  	};
|  
|  i.e. use initializers rather than assignment in a constructor.  Why?
|  The following line of code won't work with the first version, but will
|  work with the second version:
|  
|  	const Point kPoint(23);


Using Cfront 2.1 and the first definition of class Point above (the one with
assignment in the constructors), I have no trouble compiling a main that
creates const Point kPoint(23).  And, Point::x actually gets the value 23
in the definition of kPoint when I add a print member function to examine it.

	Mike Balk
	AT&T Bell Laboratories
	Murray Hill, NJ 07974
	mwb@ulysses.att.com